This chapter is dedicated to showing that variations occur in the wild, not only in domesticated conditions. He proves this in several ways. First, it is simply well-known and obvious that wild organisms do vary, often significantly, from one another and these differences are often inherited. Though these variations often affect what might be considered less essential parts of the organism, there are known cases of variation in what are certainly very important parts of the organism. For example, Darwin cites the case of research showing that the nervous system of insects can vary greatly from one individual to the next. While some might argue that "important organs" of animals are precisely those organs that do not vary, this is just a circular argument that could be easily dismissed. Any more open-minded view would be forced at accept the...